Official Answer
Answer
Relaxation is the loss of load $P$ over time while the spring is held at a constant deflection $\delta$. It is a form of creep. At temperatures above 150C, carbon steel springs lose significant preload. If an actuator requires a 500N hold-down force and the spring relaxes by 20 percent, the assembly may leak or vibrate. Troubleshooting involves measuring the load at the operating height before and after a heat-soak test. To fix this, we replace 17-7PH with Inconel X-750 or A-286 and perform a 'heat-setting' operation, where the spring is compressed at a temperature 50C higher than the operating temperature.
